Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize the touch and position of the touch on the display screen, and the computing system can interpret the touch and thereafter perform an action based on the touch event.
Touch sensor panels can be implemented as an array of pixels formed by multiple drive lines (e.g. rows) crossing over multiple sense lines (e.g. columns), where the drive and sense lines are separated by a dielectric material. In some touch sensor panels, the row and column lines can be formed on a single side of a substrate. In such touch sensor panels, both near and far electric field lines are coupled between the row and column lines of each pixel, with some of the far-field lines passing through and temporarily exiting the cover glass protecting the drive and sense lines. A finger or other object touching down on or near the touch sensor panel can shunt those exiting far-field lines to ground and effect a change in the capacitance of the pixel that can be detected as a touch event. However, because most of the electric field lines are not capable of being shunted by the finger, the signal-to-noise ratio (SNR) is limited, and the touch event detection capabilities of the pixel are reduced.